Our town had a term for that age when boys were still boys but suddenly had the fist and wrists of men. Didn't mean they had the same musculature, but they now suddenly wielded these thickened hands like hammers attached to their wiry arms. 

Until this time the fights didn't amount to much. Nobody really got hurt, or at least permanently maimed. But after this time was when a kid might throw a punch and even amaze himself at the amount of 

blood

pouring out from the other end.

I once saw a kid in this state of amazement. They looked down at their first as if they were seeing their hands for the first time. Like they say in the movies: "with great power comes great responsibility". Most teenagers took that axiom in a good way. But there were always a few bad apples.